The present invention is in the field of cathode ray tube manufacture and specifically relates to the processing of metallic components for color television tubes, such as the mounting studs used to support internal elements of the tube.
Conventional color television picture tubes include an internal metal assembly known as a shadow mask, normally attached to the glass faceplate of the tube in proximity to the phosphor screen. By means of apertures therein, this shadow mask defines the positions at which electrons may impinge upon the phosphor screen.
Although many schemes for supporting the shadow mask at an appropriate position within these tubes have been proposed, the present method of choice involves the use of metal supporting elements, commonly referred to as studs or pins, pressed into the skirt or sidewall of the glass faceplate during the faceplate manufacturing process, to which the shadow mask components are subsequently attached as the tube is made. These pins are fabricated from steel, typically a stainless steel such as titanium-stabilized No. 430 stainless steel, which closely matches the thermal expansion coefficient of the glass faceplate. Expansion matching is necessary so that the pin/glass composite is not subjected to undue thermal stresses as the faceplate is exposed to subsequent temperature excursions involved in the manufacture and subsequent use of the tube. U.S. Pat. Nos. 3,004,182 and 3,333,134 show examples of tube configurations incorporating metal pins, while U.S. Pat. No. 3,021,643 describes methods and apparatus by which metal pins may be pressed into the glass skirt portion of a television picture tube faceplate.
Although the thermal expansion coefficient of the glass making up the faceplate is closely controlled during manufacture, so that problems relating to high stress at the pin insertion locations on the faceplate would not be expected, it has been found that a significant level of faceplate breakage initiating at these locations is encountered during subsequent high-temperature faceplate and tube processing operations. This problem has now been traced to a pin surface deterioration phenomenon, occurring prior to insertion of the pin into the faceplates, wherein highly localized regions of high thermal expansion are generated on the surfaces of the pins.
It is a principal object of the present invention to provide a solution to this deterioration problem, such that pins can be provided which significantly reduce the incidence of faceplate thermal stress breakage during the television tube manufacturing process.
Other objects and advantages of the invention will become apparent from the following description thereof.